Unsalted butter, also called sweet butter, is usually used in baking or when additional salt is unwanted in a recipe. The term unsalted means no salt is added during manufacturing -- it does not mean that there is no salt at all. Foods contain natural salts in the form of sodium, and the same goes for unsalted butter. The presence of these natural salts, along with safe manufacturing practices, makes rushing the butter back to the refrigerator after use unnecessary.
Microorganisms that grow in butter are responsible for spoilage. The salts in butter are natural preservatives that slow the growth of these microorganisms, increasing shelf life. While salted butter contains added salts that make spoilage a rarity, John Bruhn, a dairy-foods processing specialist at the University of California at Davis explains in an article for “Real Simple” that the natural salts present in unsalted butter are enough to keep it from spoiling for as long as a week without refrigeration.
Butter undergoes a pasteurization process before it is packaged and transported to the supermarket. This process heats the butter to temperatures high enough to kill bacteria. Pasteurization, coupled with the fact that butter contains little water, and plenty of natural salts, makes it unlikely that eating it would cause any type of serious food-borne illness -- unrefrigerated or not, notes Douglas Holt, Ph.D., Chair of Food Science Program & State Extension Specialist for Food Safety, University of Missouri-Columbia.
If you prefer your unsalted butter soft and easily spreadable, you may prefer to store it in a butter crock on your counter instead of the refrigerator. Long before refrigeration, people stored their butter in earthenware pots. The crocks keep the butter fresh and protected from outside air. Packing butter into the lid and filling the base with water -- saltwater for unsalted butter -- creates a seal that keeps the butter at room temperatures even when the outside air is as high as 80 degrees Fahrenheit.
The U.S. Department of Agriculture recommends storing butter in the refrigerator, wrapped in its original packaging, to maintain quality. To ensure it is soft when you need it, remove the butter from the refrigerator 10 to 15 minutes before you spreading. If your refrigerator goes out during a power outage, unlike milk and eggs, butter and margarine is safe unrefrigerated for more than 2 hours.
- Real Simple: Cooking Myths Debunked
- University of Missouri Extension: Food Safety
- WebExhibits: Fresh Tasting Butter in Your Butter Crock
- James Sloss Pottery: French Butter Dish
- U.S. Department of Agriculture: How to Buy Butter
- Foodsafety.gov: Refrigerated Food and Power Outages: When to Save and When to Throw Out
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